Live Well Staged Installation of Wet Connected ESP and Related Method

ABSTRACT

An ESP assembly is broken into subassemblies to fit through a lubricator for live well deployment. A lifting device has a shaft transmission feature and associated housing rotational lock for use at the top of the first subassembly and to be left in position for engagement of the next assembly. The subassemblies can be delivered on wireline or slickline. A wet connect can be at the lower end of the initial subassembly to connect to a cable run alongside the production tubing. The ESP subassemblies all are interconnected in the live well and function as they would if assembled at the surface. The ability to break down the assembly and run it in segments lets the components fit through a length limited lubricator for live well deployment.

FIELD OF THE INVENTION

The field of the invention is installation of electric submersible pumps and more particularly, devices that enable subassembly installation to fit into a lubricator for live well deployment.

BACKGROUND OF THE INVENTION

Electric submersible pumps (ESP) are used to increase bottom hole pressure to deliver produced fluids to a well surface. These pumps are multistage centrifugal pumps with the number of stages determined by the depth of the ESP and the properties of the pumped fluids and the well configuration. As wells get deeper, with improved drilling technologies, the number of stages needed to achieve desired production has necessarily increased. The additional horsepower to drive the added stages and obtain higher discharge pressures, also by necessity, increased the length of the motor associated with the ESP.

In order to deploy ESPs in live wells utilizing wire line, the pump assembly has to pass through a lubricator. A lubricator is mounted on the well head at the surface. There are installations where the lubricator length is limited by the derrick height. Other installations may limit the lubricator length based on safety concerns or policy. Lubricator assemblies contain valves at opposed ends that can be sequentially operated to introduce the ESP components into the live well, such as with a wireline or slickline, when the bottom valve is opened and the wireline or slickline is delivered through a sealed connection near the top of the lubricator. Another more recent development is to mate a wet connect device on the lower end of the ESP assembly with the other half of the connection that is connected to a cable, run alongside the tubing that will convey the pumped fluids to the surface. This type of power/instrumentation connection has also added to the overall length of the assembly. Since there is a finite limit to the height of the lubricator supported in the derrick, or limited for safety reasons, it has become a problem to get extended length, higher horsepower, ESP assemblies inserted into live wells.

It should be noted that coiled tubing, continuous rod and jointed rod or tubing could also be utilized to deploy these ESP systems with and without lubricator type equipment. While the lubricator type applications allow these installs on live wells, the same equipment can be used on wells that have been pressure equalized/neutralized or killed.

The present invention addresses this problem with a solution that allows the overall ESP assembly to be broken down into subassemblies that will fit in a lubricator for staged deployment and final system assembly, at the downhole fixture located at or near the bottom of the production tubing. This downhole fixture being the socket portion of the wet connection device. Once run into the well, these staged subassemblies function as though the entire assembly was put together at the surface, as could be done before when the assemblies had smaller motors and fewer stages.

Those skilled in the art will better appreciate the various aspects of the invention from a review of the detailed description of the preferred embodiment and the associated drawings while understanding that the full scope of the invention is to be determined by the appended claims.

SUMMARY OF THE INVENTION

An ESP assembly is broken down into subassemblies to fit within a lubricator where a safe working length is required for live well deployment. A lifting device has a shaft transmission feature and associated housing rotational lock for use at the top of the first subassembly which is left in position for engagement of the next assembly. The subassemblies can be delivered on wireline or slickline. A wet connect can be at the lower end of the initial subassembly to connect to a cable run alongside the production tubing. The ESP subassemblies all are deployed and interconnected in the live well and function as they would if assembled at the surface. The ability to break down the assembly and run it in segments lets the components fit through a length limited lubricator for live well deployment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the lift device to run in the first subassembly into production tubing;

FIG. 2 shows the production tubing in cased hole, in section, illustrating the wet connect and screen at the lower end of the production tubing;

FIG. 3 illustrates the first subassembly to be run into the production tubing with the other half of the wet connect at its lower end;

FIG. 4 is a section view of the lift sub used at the top of the assembly in FIG. 2 to run it into the production tubing to mate with the wet connect at the lower end of the production tubing;

FIG. 5 is the next subassembly to be run into the production tubing and includes the pump and lower end shaft extension to mate into the lift sub shown in FIG. 4 that is left in the production tubing;

FIG. 6 is the last subassembly that includes a seal assembly for the production tubing;

FIG. 7 is an anchor mounted above the seal assembly of FIG. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 2, a borehole is shown with casing 10 although an open hole is an alternative. Production tubing 12 is run into the casing 10 and supports at its lower end a half 14 of a wet connection of a type known in the art. A cable for power and communication between the surface and the wet connect 14 is schematically illustrated. The assembly in FIG. 2 has the other half of the wet connect 20 at its lower end and is referred to as the socket portion of the wet connect. When the halves 14 and 20 make electrical contact such a condition is sensed at the surface through the cable 16. The assembly is retained by the lift device 26 that is shown in more detail in FIGS. 1 and 4. As shown in FIG. 1 there is a lift profile 28 where a slickline or wireline can be releasably attached in a manner known in the art. Apart from that there are anti-rotation lugs 32 in the housing 30 that are engaged by splines 34 shown at the lower end of FIG. 5 on the crossover assembly 35. Once crossover assembly 35 is landed onto lift device 26, axial load from the pump, 46 is transferred from 4-3, through 35, 26 and ultimately to the thrust bearing inside 24.

Thus, in operation, the housing 30 does not rotate but the shaft coupling assembly 36 turns. Assembly 36 is supported on bearings 38 and 40 and has a male end 42 with spline 44 to engage a pump shaft that is not shown that extends out the lower end of the ESP 46 shown in FIG. 5. One or more openings 48 are provided in housing 30 to allow solids or other debris to pass out of the housing 30 when it is run in with the assembly shown in FIG. 3. The remainder of the assembly in FIG. 3 is a lower portion of a motor module module 22 that is rotationally locked at 50 to the remainder of the motor assembly 22 and 24.

Item 24 is the seal section component. This component provides an equalization function between the well bore pressures seen at depth and the internal pressure of the ESP components 46, 58 and 60. In addition to providing pressure equalization, the seal component 24 also handles axial thrust to the ESP system created by the driven pump assembly 46 while the system is energized. The seal component 24 also protects the motor 22, 24 and connection plug 20 from well bore fluid contamination. It is important to note that the assembly of FIG. 3 must all be part of the same staged installation as they are all serviced/filled with a synthetic type of dielectric oil.

The motor shaft extends From 22 through 24 to end 52 where an end spline meshes into the female splined connection 54 shown in FIG. 1. The pump shaft, not shown is a female end that slips over the male end shaft 42 with splines 44. In essence the lift device 26 serves as a coupling between the seal shaft at end 52, and the pump crossover 35 shaft to the pump intake shaft not shown that passes through ports 66 to the shaft in pump 46 that is not shown.

Once the assembly of FIG. 2 has been deployed into the production tubing 12 of FIG. 1 and the wet connect portions 14 and 20 are communicating the wireline or slickline or other conveyance supporting the lift device 26 is released and the wireline or slickline is retrieved to the surface to allow the assembly of FIG. 5 to be picked up and run into a live well through a lubricator that is not shown. In essence FIG. 5 is the ESP 46 that has a polished bore receptacle and an internal lifting profile not shown near its upper end 56. The lifting profile allows running in the ESP 46 and the crossover assembly 35 in one trip through the lubricator. The wireline or slickline is again released so that another trip into the production tubing can be made with the sealing assembly 58, then anchor assembly 60 that can be run in on a separate wire line run. Projections 62 positioned on the exterior and adjacent interior polished bore receptacle act to centralize the assembly. The anchor 60 holds the assembly shown in FIGS. 3-7 inside the production tubing 10 to keep the assembled components fixed against the wet connection 14 at the lower end of the production tubing 10.

Those skilled in the art will appreciate the fact that the problem of limited length in a lubricator is addressed by the present invention that breaks down an overlong assembly into stages that are short enough to load into a lubricator with a length limit of about 25 meters allowing the assembly to be put together in the live well while still maintaining the safety systems that are there to prevent loss of well control. The first break location is at the motor drive shaft which is run in with the lift device 26 in a way that the motor shaft is already coupled to the lift device that is left in the hole after the first trip to deliver the assembly of FIG. 2. After making contact with the wet connect 14 already at the bottom of the production tubing 10 the conveyance such as wireline or slickline is removed and the assembly of FIG. 5 including the ESP 46 is lifted and deployed. The pump shaft that is not shown connects to spline 44 on the lift sub shaft 42. The conveyance is again released leaving exposed the polished bore receptacle on the top end 56 of the FIG. 5 assembly. The seal assembly 58 can be run in with the anchor 60 or separately. A seal assembly at the lower end of 58 registers with the polished bore receptacle that is not shown. Externally, the seal assembly 58 divides the suction and discharge sides of the EPSP 46. Suction from the formation enters through screen 64 shown in FIG. 1 and passes through inlets 66 shown in FIG. 5. Discharge flow from the ESP 46 passes through the sealing assembly 58 and the anchor 60 on up to the surface through the production tubing 12.

The problem that limits placement of ESP in a live well at depths where the length of the ESP and motor exceed the lubricator length is solved with the present invention. While the break locations in the ESP assembly can be selected at different component connections doing the breaking up at the connection of the motor shaft to the pump shaft allows more efficient use of the available length in these limited length lubricators. The incorporation of a shaft connector in the lift sub also allows having the break in the assembly at the connection between the motor and pump shafts. The other components above just push together and are finally anchored by anchor 60. As the operating depth and pressure output demanded from ESPs increases the ability to get the entire assembly into a live well will no longer be limited by lubricator length can no longer be a limiting factor. Indeed in the deeper applications where more pump stages and motor horsepower are required would mean such assemblies could not be run into a live well without significant risks of blowout. The method of the present invention allows the safe downhole assembly in a live well of long ESPs that are wet connected in the hole.

The above description is illustrative of the preferred embodiment and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below: 

We claim:
 1. A method of assembling an electric submersible pump (ESP) assembly in a live well that in the aggregate is longer than an available lubricator, comprising: assembling subassemblies that are shorter than the lubricator at the surface of a borehole; running in said subassemblies into the borehole through the lubricator; assembling said subassemblies to each other in the borehole.
 2. The method of claim 1, comprising: separating the motor driver from the ESP into separate assemblies.
 3. The method of claim 2, comprising: using a lift device connected on one end to a motor/seal driveshaft when delivering the motor driver separately from said ESP system.
 4. The method of claim 3, comprising: providing a connector shaft in said lift device connected on a lower end to said motor shaft.
 5. The method of claim 4, comprising: rotationally locking said motor shaft to said connector shaft in said lift device.
 6. The method of claim 5, comprising: engaging a pump shaft of said ESP to an opposite end of said connector shaft when the ESP assembly has passed through the lubricator.
 7. The method of claim 6, comprising: rotationally locking a housing of said lift device to a housing of said ESP on assembly.
 8. The method of claim 7, comprising: providing a male spline on an end of said connector shaft that engages the pump shaft and a female spline on the opposite end of said connector shaft that engages said motor shaft.
 9. The method of claim 1, comprising: initially installing a wet connect adjacent a lower end of a production string in the borehole; mating to said wet connect with the initial subassembly run into said production tubing.
 10. The method of claim 9, comprising: running in the initial subassembly with a lift device at its upper end; leaving said lift device in the production tubing for subsequent connection to the next delivered subassembly.
 11. The method of claim 10, comprising: delivering subassemblies on wireline or slickline or tubing.
 12. The method of claim 10, comprising: providing a lifting profile at an upper end of said lifting device.
 13. The method of claim 10, comprising: using motor driver components as the first delivered subassembly.
 14. The method of claim 13, comprising: connecting the ESP, as a second subassembly, to the lift device positioned above the first subassembly.
 15. The method of claim 14, comprising: providing a connector shaft in said lift device to connect a motor shaft to a pump shaft.
 16. The method of claim 15, comprising: rotationally locking a housing of said ESP pump to a housing on said lift device. 